1. Field of the Invention
The present invention relates to aseptic food processes. Specifically, the present invention relates to a method and apparatus for producing an aseptic heterogeneous food.
2. Description of the Related Art
Traditionally, shelf-stable soup has been packaged in a metal (tin) can due to thermal processing requirements. The soup is filled into the can and the can is sealed. The sealed can is placed on a rack with other cans, and the rack is rotated while being subjected to a predetermined temperature for sterilizing the product. Heterogeneous foods have been limited to such packaging technique because until recently this was the only process approved by the Food and Drug Administration ("FDA") for shelf-stable heterogeneous foods.
A continuous thermal process for sterilizing heterogeneous foods has recently been approved by the FDA. The process was previously used for homogeneous foods such as shelf-stable milk sold by PARMALAT.RTM. and packaged in TETRA BRIK.RTM. containers. The process maintains the heterogeneous food in a holding tube at a predetermined temperature for a predetermined time thereby effectively sterilizing the heterogeneous food.
The heterogeneous food generally consists of a viscous carrier and suspended particles. The carrier is heated by contact with the walls of the thermal process equipment, and this heat is then transferred to the suspended particles by conduction and convective heat transfer. Often, the carrier receives a thermal treatment in excess of what is necessary to sterilize it and is overcooked due to its prolonged exposure to the high temperature. The particles may also be overcooked due to the time that is required to cool the heterogeneous food using heat exchangers to a packaging temperature once the heterogeneous food has been maintained for the predetermined time period at the predetermined temperature in the holding tube.
The FDA approval for this process requires that the heterogeneous food be maintained for the predetermined time period at the predetermined temperature in the holding tube. Thus, any attempt to cool the heterogeneous food must be able to include that holding tube time period while maintaining the aseptic nature of the processing system. This problem has not previously been addressed by the packaging industry because of the lack of FDA approval for a continuous processing system until recently.